Device, Network, and Method for Communications with Spatial-specific Sensing

ABSTRACT

A device, a network, and a method for wireless communication are provided. In an embodiment, the method, performed by a first communication node, includes generating at least one of a spatial-specific receiving pattern and a first spatial-specific processing pattern, receiving a waveform signal from one or more second nodes in accordance with the at least one of the spatial-specific receiving pattern or the first spatial-specific processing pattern, determining a second spatial-specific processing pattern and a channel status of a channel, wherein the channel status of the channel is according to the at least one of the spatial-specific receiving pattern and the second spatial-specific processing pattern and transmitting a signal along a transmission direction, wherein the transmission direction is in accordance with the at least one of the spatial-specific receiving pattern and the second spatial-specific processing pattern.

This is a continuation of U.S. patent application Ser. No. 14/810,299entitled “Device, Network, and Method for Communications withSpatial-specific Sensing,” filed Jul. 27, 2015, which application claimsthe benefit of U.S. Provisional Patent Application No. 62/030,457 filedJul. 29, 2014 and entitled “Device, Network, and Method forCommunications with Spatial-specific Sensing,” which applications areincorporated herein by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to a device, network, and method forwireless communications, and, in particular embodiments, to a device,network, and method for communications with sensing in the spatialdomain, i.e., directional sensing, or more generally, resource-specificsensing.

BACKGROUND

The amount of wireless data being transferred is expected to exceed thatof wired data, pushing the limits of macro cellular deployment. Smallcell deployment with higher density and/or with new and diversifiedspectrum resources may be used to help handle this increase in datacapacity, while meeting customer quality of service expectations andoperators' requirements for cost-effective service delivery.

Small cells generally are low-power wireless access points that operatein a licensed spectrum. Small cells provide improved cellular coverage,capacity and applications for homes and businesses, as well asmetropolitan and rural public spaces. Different types of small cellsinclude, generally from smallest size to largest size, femtocells,picocells, and microcells. Small cells may be densely deployed and mayalso utilize additional spectrum resources, such as spectrum resourcesin high-frequency bands operating in millimeter wave (mmWave) regime,unlicensed/shared-license spectrum resources, etc.

SUMMARY

Various embodiments relate to devices, networks, and methods forcommunications with sensing in the spatial domain.

An embodiment method for providing contention-based transmission from afirst communication node in a network to a second communication nodeincludes determining, by the first communication node, a transmissiondirection, the transmission direction characterized by a digitalbeamforming direction and an analog beamsteering direction; performing,by the first communication node, spatial-specific carrier sensing inaccordance with a sensing direction associated with the transmissiondirection; determining, by the first communication node, a channelstatus of a channel along the sensing direction according to thespatial-specific carrier sensing; and transmitting, by the firstcommunication node, a signal along the transmission direction when thechannel is not busy.

An embodiment first communication node for providing contention-basedtransmission from a first communication node in a network to a secondcommunication node includes a processor and a non-transitory computerreadable storage medium storing programming for execution by theprocessor, the programming including instructions to: determine atransmission direction, the transmission direction characterized by adigital beamforming direction and an analog beamsteering direction;perform spatial-specific carrier sensing in accordance with a sensingdirection associated with the transmission direction; determine achannel status of a channel along the sensing direction according to thespatial-specific carrier sensing; and transmit a signal along thetransmission direction when the channel is not busy.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawing, in which:

FIG. 1A illustrates cellular communications in a macro cell;

FIG. 1B illustrates cellular communications in a heterogeneous networkwith a macro cell and a pico cell;

FIG. 1C illustrates cellular communications in a macro cell with carrieraggregation;

FIG. 1D illustrates cellular communications in a heterogeneous networkwith a macro cell and several small cells;

FIG. 1E illustrates an example dual connectivity scenario;

FIG. 2A illustrates example orthogonal frequency division multiplexing(OFDM) symbols with normal cyclic prefix (CP);

FIG. 2B illustrates an example frame structure for a frequency divisionduplexing (FDD) configuration and a time division duplexing (TDD)configuration;

FIG. 2C illustrates an example OFDM subframe for FDD configuration;

FIG. 2D illustrates an example OFDM subframe for TDD configuration;

FIG. 2E illustrates an example common reference signal (CRS);

FIG. 2F illustrates an example channel status indicator reference signal(CSI-RS) and dedicated/de-modulation reference signal (DMRS);

FIG. 2G illustrates an example of transmission power;

FIGS. 3A and 3B are block diagrams of embodiments of systems 300, 350for analog beamsteering;

FIG. 4 illustrates an example of Frame based equipment operating inunlicensed spectrum;

FIG. 5 is a flowchart for an example of traditional carrier sensing;

FIG. 6 is a flowchart for an example of traditional listen-before-talkmechanism;

FIG. 7 illustrates a channel access procedure for WiFi;

FIGS. 8A-8B illustrate an example of antenna pattern with a normal(wide) beam (A) and an example of antenna pattern with a narrow beam(B);

FIG. 9 illustrates an example of multiple nodes accessing a carrierusing traditional listen-before-talk mechanism;

FIG. 10 illustrates an example of multiple nodes accessing a carrier innarrow-beam setting;

FIG. 11 illustrates an example of two (transmitted or received) beams ata nodes;

FIG. 12 is a flowchart for an example of spatial-resource-specificcarrier sensing;

FIG. 13 is a flowchart for an example of spatial-resource-specificlisten-before-talk mechanism;

FIG. 14 illustrates a block diagram of an embodiment processing systemperforming methods described herein, which may be installed in a hostdevice; and

FIG. 15 illustrates a block diagram of a transceiver adapted to transmitand receive signaling over a telecommunications network.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments arediscussed in detail below. It should be appreciated, however, that thepresent disclosure provides many applicable inventive concepts that canbe embodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the disclosure, and do not limit the scope of the disclosure.

Typically, in a modern wireless communications system, such as a ThirdGeneration Partnership Project (3GPP) Long Term Evolution (LTE)compliant communications system, a plurality of cells or evolved NodeBs(eNBs) (also commonly referred to as NodeBs, base stations (BSs), baseterminal stations, communications controllers, network controllers,controllers, access points (APs), and so on) may be arranged into acluster of cells, with each cell having multiple transmit antennas.Additionally, each cell or eNB may be serving a number of users (alsocommonly referred to as User Equipment (UEs), wireless devices, mobilestations, users, subscribers, terminals, and so forth) based on apriority metric, such as fairness, proportional fairness, round robin,and the like, over a period of time. It is noted that the terms cell,transmission points, and eNB may be used interchangeably. Distinctionbetween cells, transmission points, and eNBs will be made where needed.

As shown in FIG. 1A, system 100 is a typical wireless network with acommunications controller 105 communicating using a wireless link 106 toa first wireless device 101 and a second wireless device 102. Thewireless link 106 can comprise a single carrier frequency such as usedtypically for a time division duplex (TDD) configuration or a pair ofcarrier frequencies as used in a frequency division duplex (FDD)configuration. Not shown in system 100 are some of the network elementsused to support the communications controller 105 such as a backhaul,management entities, etc. The transmission/reception from controller toa UE is called downlink (DL) transmission/reception, and thetransmission/reception from a UE to a controller is called uplink (UL)transmission/reception. The communication controller 105 may include anantenna, a transmitter, a receiver, a processor, and non-transitorycomputer readable storage and/or memory. The communication controller105 may be implemented as or referred to as a transmission point (TP),BS, a base transceiver station (BTS), an AP, an eNB, a networkcontroller, a controller, a base terminal station, and so on. Theseterms may be used interchangeably throughout this disclosure.

As shown in FIG. 1B, system 120 is an example wireless heterogeneousnetwork (HetNet) with communications controller 105 communicating towireless device 101 using wireless link 106 (solid line) and to wirelessdevice 102 using wireless link 106. A second communications controller121, such as a pico cell, has a coverage area 123 and is capable ofcommunicating to wireless device 102 using wireless link 122. Typically,wireless link 122 and wireless link 106 use the same carrier frequency,but wireless link 122 and wireless link 106 can use differentfrequencies. There may be a backhaul (not shown) connectingcommunications controller 105 and communications controller 121. AHetNet may include a macro cell and a pico cell, or generally a higherpower node/antenna with a larger coverage and lower power node/antennaswith a smaller coverage. Lower power nodes (or lower power points,picos, femtos, micros, relay nodes, remote radio heads (RRHs), remoteradio units, distributed antennas, etc.) generally are low-powerwireless access points that operate in a licensed spectrum. Small cellsmay use lower power nodes. Lower power nodes provide improved cellularcoverage, capacity and applications for homes and businesses, as well asmetropolitan and rural public spaces.

In a network such as system 120 in FIG. 1B, there may be multiple macropoints 105 and multiple pico points 121 operating with multiplecomponent carriers, and the backhaul between any two points can be fastbackhaul or slow backhaul depending on the deployment. When two pointshave fast backhaul, the fast backhaul may be fully utilized, e.g., tosimplify the communication method and system or to improve coordination.In a network, the points configured for a UE for transmission orreception may include multiple points, some pairs of points may havefast backhaul, but some other pairs of points may have slow backhaul orany backhaul.

In a deployment, an eNodeB may control one or more cells. Multipleremote radio units may be connected to the same base band unit of theeNodeB by fiber cable, and the latency between base band unit and remoteradio unit is quite small. Therefore the same base band unit can processthe coordinated transmission/reception of multiple cells. For example,the eNodeB may coordinate the transmissions of multiple cells to a UE,which is called coordinated multiple point (CoMP) transmission. TheeNodeB may also coordinate the reception of multiple cells from a UE,which is called CoMP reception. In this case, the backhaul link betweenthese cells with the same eNodeB is fast backhaul and the scheduling ofdata transmitted in different cells for the UE can be easily coordinatedin the same eNodeB.

As an extension of the HetNet deployment, possibly densely deployedsmall cells using low power nodes are considered promising to cope withmobile traffic explosion, especially for hotspot deployments in indoorand outdoor scenarios. A low-power node generally means a node whosetransmission power is lower than macro node and BS classes, for examplePico and Femto eNB are both applicable. Small cell enhancements forE-UTRA and E-UTRAN, which is an ongoing study in 3GPP, will focus onadditional functionalities for enhanced performance in hotspot areas forindoor and outdoor using possibly densely deployed low power nodes.

As shown in FIG. 1C, system no is a typical wireless network configuredwith carrier aggregation (CA) where communications controller 105communicates to wireless device 101 using wireless link 106 (solid line)and to wireless device 102 using wireless link 107 (dashed line) andwireless link 106. In some example deployments, for wireless device 102,wireless link 106 can be called a primary component carrier (PCC) whilewireless link 107 can be called a secondary component carrier (SCC). Insome carrier aggregation deployments, the PCC can be provided feedbackfrom a wireless device to a communications controller while the SCC cancarry data traffic. In the 3GPP Rel-10 specification, a componentcarrier is called a cell. When multiple cells are controlled by a sameeNodeB, cross scheduling of multiple cells is possible to be implementedbecause there may be a single scheduler in the same eNodeB to schedulethe multiple cells. With CA, one eNB may operate and control severalcomponent carriers forming primary cell (Pcell) and secondary cell(Scell). In Rel-11 design, an eNodeB may control both a Macro cell and aPico cell. In this case, the backhaul between the Macro cell and thePico cell is fast backhaul. The eNodeB can control thetransmission/reception of both macro cell and Pico cell dynamically.

As shown in FIG. 1D, system 130 is an example wireless heterogeneousnetwork with communications controller 105 communicating to wirelessdevice 101 using wireless link 106 (solid line) and to wireless device102 using wireless link 106. A second communications controller 131,such as a small cell, has a coverage area 133 and is capable ofcommunicating to wireless device 102 using wireless link 132. Acommunications controller for another small cell 135 has coverage area138 and uses wireless link 136. Communications controller 135 is capableof communicating to wireless device 102 using wireless link 136.Coverage areas 133 and 138 may overlap. The carrier frequencies forwireless links 106, 132, and 136 may be the same or may be different.

FIG. 1E shows an example system configured for dual connectivity. Amaster eNB (MeNB) is connected to one or more secondary eNBs (SeNBs)using an interface such as the Xn interface (Xn can be X2 in somespecific cases). The backhaul can support this interface. Between theSeNBs, there may be an X2 interface. A UE, such as UE1, is connectedwirelessly to MeNB1 and SeNB1. A second UE, UE2, can connect wirelesslyto MeNB1 and SeNB2.

In orthogonal frequency-division multiplexing (OFDM) systems, thefrequency bandwidth is divided into multiple subcarriers in frequencydomain. In the time domain, one subframe is divided into multiple OFDMsymbols. Each OFDM symbol may have a cyclic prefix to avoid theinter-symbol interference due to multiple path delays. One resourceelement (RE) is defined by the time-frequency resource within onesubcarrier and one OFDM symbol. A reference signal and other signals,such as a data channel, e.g. physical downlink shared channel (PDSCH),and a control channel, e.g. physical downlink control channel (PDCCH),are orthogonal and multiplexed in different resource elements intime-frequency domain. Further, the signals are modulated and mappedinto resource elements. For each OFDM symbol, the signals in thefrequency domain are transformed into the signals in time domain using,e.g., Fourier transforms, and are transmitted with added cyclic prefixto avoid the inter-symbol interference.

Each resource block (RB) contains a number of REs. FIG. 2A illustratesexample OFDM symbols with normal cyclic prefix (CP). There are 14 OFDMsymbols labeled from 0 to 13 in each subframe. The symbols 0 to 6 ineach subframe correspond to even numbered slots, and the symbols 7 to 13in each subframe correspond to odd numbered slots. In the figure, onlyone slot of a subframe is shown. There are 12 subcarriers labeled from 0to 11 in each RB, and hence in this example, there are 12×14=168 REs ina RB pair (an RB is 12 subcarriers by the number of symbols in a slot).In each subframe, there are a number of RBs, and the number may dependon the bandwidth (BW).

FIG. 2B shows two frame configurations used in LTE. Frame 200 istypically used for a FDD configuration, where all 10 subframes, labeled0 through 9, communicate in the same direction (downlink in thisexample). Each subframe is 1 millisecond in duration and each frame is10 milliseconds in duration. Frame 210 shows a TDD configuration wherecertain subframes are allocated for downlink transmissions (such asunshaded boxes (subframes 0 and 5), for uplink transmissions (verticallines (subframe 2)), and special (dotted box (subframe 1)) which containboth uplink and downlink transmissions. An entire subframe dedicated fordownlink (uplink) transmission can be called a downlink (uplink)subframe. Subframe 6 can be either a downlink or a special subframedepending on TDD configuration. Each of the solid shaded boxes(subframes 3, 4, 7, 8, and 9) can be either a downlink subframe or anuplink subframe depending on TDD configuration. The coloring used inframe 210 is exemplary but is based on the standards TSG 36.211 Rel. 11,which is hereby incorporated herein by reference.

FIG. 2C and FIG. 2D show examples of downlink subframes that arepartitioned in terms of symbols and frequency. A subframe, such assubframe 205, is divided into 3 sections in the frequency domain(assuming the number of RBs is greater than 6). An analogous diagram canbe shown for a 6 RBs downlink bandwidth (e.g., bandwidth of the downlinkcarrier).

In FIG. 2C, subframe 205 shows an example of the symbol allocation foran FDD configuration for subframes 0 and 5. The solid shading shows thesymbols that have the common reference signal (CRS). The example assumeseither CRS is transmitted on antenna port 0 or on antenna ports 0 and 1.The horizontal shading shows the location of the secondarysynchronization signal (SSS). The dotted shading shows the location ofthe primary synchronization signal (PSS). Both the PSS and SSS occupythe center six resource blocks of the downlink carrier. The diagonallines in symbols 0, 1, 2, 3 of slot 1 represent the location where thephysical broadcast channel (PBCH) occupies for subframe 0. The PBCH isnot transmitted in subframe 5 in Rel. 11 of the standards. Note, thePSS, SSS, and CRS can be viewed as overhead.

In FIG. 2D, subframe 215 shows an example of the symbol allocation forsubframes 0 and 5 of TDD subframe 210 in FIG. 2B. Likewise, subframe 218shows an example of the symbol allocation for subframes 1 and 6 of TDDsubframe 210. In both subframe 215 and subframe 218, the solid shadingshows the symbols having the CRS. The example also assumes either CRS istransmitted on antenna port 0 or on antenna ports 0 and 1. Thehorizontal shading in subframe 215 shows the location of the SSS. Thedotted shading in subframe 218 shows the location of the PSS. Both thePSS and SSS occupy the center six RBs of the downlink carrier. The crossshading in subframe 218 indicates that the remaining symbols of thesubframe are either downlink (if subframe 6 is a downlink subframe) or acombination of downlink symbols, guard time, and uplink symbols if thesubframe is a special subframe. Similar to FIG. 2C, the diagonal linesin symbols 0, 1, 2, 3 of slot 1 represent the location where the PBCHoccupies for subframe 0. The PBCH is not transmitted in subframe 5 inRel. 11 of the standards. Note, the PSS, SSS, and CRS can be viewed asoverhead. The information contents of the PBCH (i.e., master informationblock) can change every 40 ms.

In downlink transmission of LTE-A system, there is reference signal forUE to perform channel estimation for demodulation of PDCCH and othercommon channels as well as for measurement and some feedbacks, which isCRS inherited from the Rel-8/9 specification of E-UTRA, as shown in FIG.2E. Dedicated/de-modulation reference signal (DMRS) can be transmittedtogether with the PDSCH channel in Rel-10 of E-UTRA. DMRS is used forchannel estimation during PDSCH demodulation. DMRS can also betransmitted together with the enhanced PDCCH (EPDCCH) for the channelestimation of EPDCCH by the UE. The notation (E)PDCCH indicates EPDCCHand/or PDCCH.

In Rel-10, channel status indicator reference signal (CSI-RS) isintroduced in addition to CRS and DMRS, as shown in FIG. 2F. CSI-RS isused for Rel-10 UEs to measure the channel status, especially formultiple antennas cases. PMI/CQI/RI and other feedback may be based onthe measurement of CSI-RS for Rel-10 and beyond UE. PMI is the precodingmatrix indicator, CQI is the channel quality indicator, and RI is therank indicator of the precoding matrix. There may be multiple CSI-RSresources configured for a UE. There is specific time-frequency resourceand scrambling code assigned by the eNB for each CSI-RS resource.

FIG. 2G shows an exemplary plot 220 of the transmission power from acommunications controller, such as 105 in FIG. 1A, for a FDDconfiguration for subframes 0 and 1. Plot 220 shows the communicationcontroller still transmits signals such as the CRS (solid shading), theSSS (horizontal shading), the PSS (dotted shading), and the PBCH(diagonal shading) even if there is no other data to transmit on thedownlink. The transmission of these signals can increase theinterference observed in a system such as in FIG. 1B even whencommunications controller 121 is not serving a UE such as wirelessdevice 102. This interference can reduce the system capacity.

However, eliminating these signals entirely can impair system operation.For example, a wireless device relies on these signals to synchronize(both time and frequency) and then make measurements.

One concept to reduce the interference from eNBs without any UEsattached (assigned, camped) is to turn those eNBs off. When UEs arrive,the eNBs would then turn on. Likewise, when there is no more traffic,the eNBs could then turn off. However, there are many modifications tothe standards in order to support the on-off mechanism (on/offadaptation) such as the UE identifying the quality of an eNB based onthe persistent transmission of signals such as the PSS, SSS, and CRS;when those signals are absent, how the UE can measure the quality. Otherquestions regarding small cell on/off adaptation, or more generally,network adaptation, include:

1. Coverage issue: ensuring cellular coverage despite of small cellon/off;

2. Idle UE issue: can small cell operating on/off support UEs in theidle state, what needs to be done to support idle UEs, in the connectedstate can the UE/eNB exchange data;

3. Legacy UE support (how to support UEs that do not have this feature);

4. How may fast on/off adaptation be supported? More specifically, howmay fast on/off adaptation be supported, given newly introducedprocedures/mechanisms (in Rel-11/12 or even beyond) such as small celldiscovery and measurement enhancements; dual connectivity or morebroadly, multi-stream aggregation (MSA); CoMP and enhanced CoMP (eCoMP)(including CoMP Scenario 4 (a network with low power RRHs within themacrocell coverage where the transmission/reception points created bythe RRHs have the same cell IDs as the macro cell), coordination overnon-ideal backhaul); massive carrier aggregation, etc.

Typical deployment scenarios include a coverage layer whose cells do notperform network adaptation (or at least not too frequently orsignificantly), and a capacity layer whose cells (mainly small cells)may perform network adaptation. Coverage/mobility and idle UE supportare mainly provided by the coverage layer. Typically UEs connect tocells in the coverage layer first, and then connect to small cells inthe capacity layer when needed. The small cells may be co-channel ornon-co-channel with those in the coverage layer. One example deploymentis shown in FIG. 1E.

In an embodiment, as one efficient way to deploy and operate the smallcells, a virtual cell configuration (e.g., CoMP Scenario 4) is adopted,and the small cells are configured and turned on opportunistically forUEs with high traffic demand. Thus, in such a network, coverage and idleUE support are ensured and not affected by small cell adaptation.

The mechanism of dynamic on/off of a small cell is seen as morebeneficial when further evolution of the small cell networks isenvisioned. Specifically, to handle the ever increasing needs in datacapacity, while meeting customer quality of service expectations andoperators' requirements for cost-effective service delivery, thedensification of a small cell network is proposed. Roughly speaking,doubling the density of the small cell network can yield doubling of thecapacity of the network. However, densification leads to higherinterference, especially the interference caused by common channels(e.g. CRS) which are persistently transmitted. Turning off the smallcell opportunistically can significantly help reduce interference andimprove efficiency of the dense network.

In parallel with increasing the network resources by densifying thenetwork, another way to increase the network resources is to utilizemore and more usable spectrum resources, which include not only thelicensed spectrum resources of the same type as the macro, but also thelicensed spectrum resources of different type as the macro (e.g., themacro is a FDD cell but a small cell may use both FDD and TDD carriers),as well as unlicensed spectrum resources and shared-licensed spectrums;some of the spectrum resources lie in high-frequency bands, such as 6GHz to 60 GHz. The unlicensed spectrums can be used by generally anyuser, subject to regulation requirements. The shared-licensed spectrumsare also not exclusive for an operator to use. Traditionally theunlicensed spectrums are not used by cellular networks as it isgenerally difficult to ensure quality of service (QoS) requirements.Operating on the unlicensed spectrums mainly include wireless local areanetworks (WLAN), e.g. the Wi-Fi networks. Due to the fact that thelicensed spectrum is generally scarce and expensive, utilizing theunlicensed spectrum by the cellular operator may be considered. Notethat on high-frequency bands and unlicensed/shared-licensed bands,typically TDD is used and hence the channel reciprocity can be exploitedfor the communications.

On unlicensed spectrum, generally there is no pre-coordination amongmultiple nodes operating on the same frequency resources. Thus, acontention-based protocol (CBP) may be used. According to Section 90.7of Part 90 (paragraph 58) of the United States Federal CommunicationCommission (FCC), CBP is defined as:

CBP—“A protocol that allows multiple users to share the same spectrum bydefining the events that must occur when two or more transmittersattempt to simultaneously access the same channel and establishing rulesby which a transmitter provides reasonable opportunities for othertransmitters to operate. Such a protocol may consist of procedures forinitiating new transmissions, procedures for determining the state ofthe channel (available or unavailable), and procedures for managingretransmissions in the event of a busy channel.” Note that the state ofa channel being busy may also be called as channel unavailable, channelnot clear, channel being occupied, etc., and the state of a channelbeing idle may also be called as channel available, channel clear,channel not occupied, etc.

One of the most used CBP is the “listen before talk” (LBT) operatingprocedure in IEEE 802.11 or WiFi (which can be found in, e.g., “WirelessLAN medium access control (MAC) and physical layer (PHY)specifications,” IEEE Std 802.11-2007 (Revision of IEEE Std802.11-1999)), which is hereby incorporated herein by reference. It isalso known as the carrier sense multiple access with collision avoidance(CSMA/CA) protocol. Carrier sensing is performed before any transmissionattempt, and the transmission is performed only if the carrier is sensedto be idle, otherwise a random backoff time for the next sensing isapplied. The sensing is generally done through a clear channelassessment (CCA) procedure to determine if the in-channel power is belowa given threshold.

In ETSI EN 301 893 V1.7.1, which is hereby incorporated herein byreference, Clause 4.9.2, it describes 2 types of Adaptive equipment:Frame Based Equipment and Load Based Equipment. To quote thespecification:

“Frame Based Equipment shall comply with the following requirements:

1) Before starting transmissions on an Operating Channel, the equipmentshall perform a Clear Channel Assessment (CCA) check using “energydetect”. The equipment shall observe the Operating Channel(s) for theduration of the CCA observation time which shall be not less than 20 μs.The CCA observation time used by the equipment shall be declared by themanufacturer. The Operating Channel shall be considered occupied if theenergy level in the channel exceeds the threshold corresponding to thepower level given in point 5 below. If the equipment finds the OperatingChannel(s) to be clear, it may transmit immediately (see point 3 below).

2) If the equipment finds an Operating Channel occupied, it shall nottransmit on that channel during the next Fixed Frame Period.

NOTE 1: The equipment is allowed to continue Short Control SignallingTransmissions on this channel providing it complies with therequirements in clause 4.9.2.3.

NOTE 2: For equipment having simultaneous transmissions on multiple(adjacent or non-adjacent) Operating Channels, the equipment is allowedto continue transmissions on other Operating Channels providing the CCAcheck did not detect any signals on those channels.

3) The total time during which an equipment has transmissions on a givenchannel without re-evaluating the availability of that channel, isdefined as the Channel Occupancy Time. The Channel Occupancy Time shallbe in the range 1 ms to 10 ms and the minimum Idle Period shall be atleast 5% of the Channel Occupancy Time used by the equipment for thecurrent Fixed Frame Period. Towards the end of the Idle Period, theequipment shall perform a new CCA as described in point 1 above.

4) The equipment, upon correct reception of a packet which was intendedfor this equipment, can skip CCA and immediately (see note 3) proceedwith the transmission of management and control frames (e.g. ACK andBlock ACK frames). A consecutive sequence of such transmissions by theequipment, without it performing a new CCA, shall not exceed the MaximumChannel Occupancy Time as defined in point 3 above.

NOTE 3: For the purpose of multi-cast, the ACK transmissions (associatedwith the same data packet) of the individual devices are allowed to takeplace in a sequence.

5) The energy detection threshold for the CCA shall be proportional tothe maximum transmit power (P_(H)) of the transmitter: for a 23 dBme.i.r.p. transmitter the CCA threshold level (TL) shall be equal orlower than −73 dBm/MHz at the input to the receiver (assuming a 0 dBireceive antenna). For other transmit power levels, the CCA thresholdlevel TL shall be calculated using the formula: TL=−73 dBm/MHz+23−P_(H)(assuming a 0 dBi receive antenna and P_(H) specified in dBm e.i.r.p.).”

“Load based Equipment may implement an LBT based spectrum sharingmechanism based on the Clear Channel Assessment (CCA) mode using “energydetect”, as described in IEEE 802.11™-2007 [9], clauses 9 and 17, inIEEE 802.11n™-2009 [10], clauses 9, 11 and 20 providing they comply withthe conformance requirements referred to in clause 4.9.3 (see note 1)(all of which are hereby incorporated herein by reference).

NOTE 1: It is intended also to allow a mechanism based on the ClearChannel Assessment (CCA) mode using “energy detect” as described in IEEE802.11ac™ [1.2], clauses 8, 9, 10 and 22 (which are hereby incorporatedherein by reference), when this becomes available.

Load Based Equipment not using any of the mechanisms referenced aboveshall comply with the following minimum set of requirements:

1) Before a transmission or a burst of transmissions on an OperatingChannel, the equipment shall perform a Clear Channel Assessment (CCA)check using “energy detect”. The equipment shall observe the OperatingChannel(s) for the duration of the CCA observation time which shall benot less than 20 μs. The CCA observation time used by the equipmentshall be declared by the manufacturer. The Operating Channel shall beconsidered occupied if the energy level in the channel exceeds thethreshold corresponding to the power level given in point 5 below. Ifthe equipment finds the channel to be clear, it may transmit immediately(see point 3 below).

2) If the equipment finds an Operating Channel occupied, it shall nottransmit in that channel. The equipment shall perform an Extended CCAcheck in which the Operating Channel is observed for the duration of arandom factor N multiplied by the CCA observation time. N defines thenumber of clear idle slots resulting in a total Idle Period that need tobe observed before initiation of the transmission. The value of N shallbe randomly selected in the range 1 . . . q every time an Extended CCAis required and the value stored in a counter. The value of q isselected by the manufacturer in the range 4 . . . 32. This selectedvalue shall be declared by the manufacturer (see clause 5.3.1 q)). Thecounter is decremented every time a CCA slot is considered to be“unoccupied”. When the counter reaches zero, the equipment may transmit.

NOTE 2: The equipment is allowed to continue Short Control SignallingTransmissions on this channel providing it complies with therequirements in clause 4.9.2.3.

NOTE 3: For equipment having simultaneous transmissions on multiple(adjacent or non-adjacent) operating channels, the equipment is allowedto continue transmissions on other Operating Channels providing the CCAcheck did not detect any signals on those channels.

3) The total time that an equipment makes use of an Operating Channel isthe Maximum Channel Occupancy Time which shall be less than ( 13/32)×qms, with q as defined in point 2 above, after which the device shallperform the Extended CCA described in point 2 above.

4) The equipment, upon correct reception of a packet which was intendedfor this equipment, can skip CCA and immediately (see note 4) proceedwith the transmission of management and control frames (e.g. ACK andBlock ACK frames). A consecutive sequence of transmissions by theequipment, without it performing a new CCA, shall not exceed the MaximumChannel Occupancy Time as defined in point 3 above.

NOTE 4: For the purpose of multi-cast, the ACK transmissions (associatedwith the same data packet) of the individual devices are allowed to takeplace in a sequence.

5) The energy detection threshold for the CCA shall be proportional tothe maximum transmit power (P_(H)) of the transmitter: for a 23 dBme.i.r.p. transmitter the CCA threshold level (TL) shall be equal orlower than −73 dBm/MHz at the input to the receiver (assuming a 0 dBireceive antenna). For other transmit power levels, the CCA thresholdlevel TL shall be calculated using the formula: TL=−73 dBm/MHz+23−P_(H)(assuming a 0 dBi receive antenna and P_(H) specified in dBm e.i.r.p.).”

FIGS. 3A and 3B are block diagrams of embodiments of systems 300, 350for analog beamsteering plus digital beamforming. System 300 in FIG. 3Aincludes a baseband component 302 for digital processing, a plurality ofRF chain components 304, a plurality of phase shifters 306, a pluralityof combiners 308, and a plurality of antennas 310. The diagram may beused for transmission or receiving. For simplicity, we describe thediagram assuming this is for transmission; receiving may be understoodsimilarly. Each RF chain 304 receives a weighting factor (or weight, p₁,. . . , p_(m) as shown in the figure) from the baseband component 302.The collection of the weighting factors form the digital precodingvector, precoding matrix, beamforming vector, or beamforming matrix forthe transmission. For example, a precoding vector may be [p₁, . . . ,p_(m)]. When multiple layers/streams are transmitted, a precoding matrixmay be used by the baseband unit to generate the weighting factors,which each column (or row) of the matrix is applied to a layer/stream ofthe transmission. Each RF chain 304 is coupled to a plurality of phaseshifters 306. The phase shifters may, theoretically, apply any phaseshift values, but generally in practice, only a few possible phase shiftvalues, e.g., 16 or 32 values. Each RF chain 304 generates a narrow beam312 oriented in a direction determined by the settings on the phaseshifters 306 and combiners 308. If the phase shifters can apply anyphase shift values, the beam may point to any direction, but if only afew phase shift values can be the beam may be one of few possibilities(e.g., in the figure, the solid narrow beam is selected by setting aspecific phase shift value in the RF chain, and the beam is among allthe possible narrow beams shown as solid and dotted beams correspondingto all the possible phase shift values). Each RF chain selects such anarrow beam, and all such narrow beams selected by all the RF chainswill be further superposed. How the superposition is done is based onthe digital weighting factors. The factor can make a beam from a RFchain stronger or weaker, and therefore, a different set of the factorscan generate different superpositions in the spatial domain; in thefigure, a particular beam 314 is illustrated. In other words, byselecting different digital weighting factors, different beam 314 can begenerated. The digital operations may generally refer to as (digital)beamforming or precoding, and the analog operations as (analog)beamsteering or phase shifting, but sometimes there is no cleardistinctions.

System 350 in FIG. 3B is similar to system 300 in FIG. 3A except thatcorresponding combiners 308 in each RF chain 302 are connected to oneanother.

An example of timing 400 for Frame Base Equipment is illustrated in FIG.4. An example of the flow chart for an embodiment method 500 for carriersensing is illustrated in FIG. 5. A flow chart of an embodiment method600 for a general listen-before-talk mechanism is illustrated in FIG. 6.

Referring now to FIG. 5, the method 500 begins at block 502 where thecommunication controller receives a waveform signal from a UE. At block504, the communication controller processes the signal and generates adecision variable, X. The signal processing here, in general done in thedigital domain which is normally performed in baseband, may includesampling, A/D conversion, receiver's digital combining with precodingweighting, etc. The decision variable, X, is used to determine whetherthe channel is idle or busy. At block 506, the communication controllerdetermines whether the decision variable is less than a threshold, T.The threshold may be a standardized value, or derived from a standard orsome regulation, which may be device type specific, spatial specific,etc. The threshold may also be allowed to change within a specifiedrange according to the traffic loads, interference conditions, etc. If,at block 506, the communication controller determines that the value ofthe decision variable, X, is less than the threshold, T, the method 500proceeds to block 508 where the communication controller determines thatthe carrier channel is idle, after which, the method 500 ends. If, atblock 506, the communication controller determines that the value of thedecision variable, X, is not less than the threshold, T, then the method500 proceeds to block 510 where the communication controller determinesthat the carrier channel is busy, after which, the method 500 ends.

Referring now to FIG. 6, the method 600 begins at block 602 where thecommunication controller assembles a frame. At block 604, thecommunication controller performs carrier sensing, such as describedabove with reference to FIG. 5, to determine if the channel is idle. If,at block 604, the communication controller determines that the channelis not idle, but is busy, then the method 600 proceeds to block 606where the communication controller refrains from transmitting the frameand waits for a random backoff timer to expire, after which, the methodreturns to block 604. If, at block 604, the communication controllerdetermines that the channel is idle, then the method 600 proceeds toblock 608 where the communication controller transmits the frame, afterwhich, the method ends.

WiFi is the most eminent example of applying the listen-before-talkmechanism. WiFi uses 802.11 standards technologies such as the airinterface (including physical and MAC layer). In 802.11, thecommunication channel is shared by stations under a mechanism calleddistributed channel access with a function called DCF (distributedcoordination function), which uses CSMA/CA. The DCF uses both physicaland virtual carrier sense functions to determine the state of themedium. The physical carrier sense resides in the PHY and uses energydetection and preamble detection with frame length deferral to determinewhen the medium is busy. The virtual carrier sense resides in the MACand uses reservation information carried in the Duration field of theMAC headers announcing impeding use of the wireless channel. The virtualcarrier sense mechanism is called the network allocation vector (NAV).The wireless channel is determined to be idle only when both thephysical and virtual carrier sense mechanisms indicate it to be so. Astation with a data frame for transmission first performs a CCA bysensing the wireless channel for a fixed duration, i.e., the DCFinter-frame space (DIFS). If the wireless channel is busy, the stationwaits until the channel becomes idle, defers for a DIFS, and then waitsfor a further random backoff period (by setting the backoff timer withan integer number of slots). The backoff timer decreases by one forevery idle slot and freezes when the channel is sensed busy. When thebackoff timer reaches zero, the station starts data transmission. Thechannel access procedure 700 is shown in FIG. 7.

To meet the regulatory requirements of operating in the unlicensedspectrum and to co-exist with other radio access technologies (RATs)such as Wi-Fi, the transmissions on the unlicensed spectrum cannot becontinuous or persistent in time. Rather, on/off, or opportunistictransmissions and measurements on demand may be adopted.

In addition, for operations in high-frequency bands, especially in thebands at 28 GHz to 60 GHz, they generally belong to the mmWave regime,which has quite different propagation characteristics from microwave(generally below 6 GHz). For example, mmWave experiences higher pathlossover distance than microwave does. Therefore, high-frequency bands aremore suitable for small cell operations than macro cell operations, andthey generally rely on beamforming with a large number of antennas(e.g. >16, and sometimes maybe even a few hundred) for effectivetransmissions. Note that at high frequency, the wavelengths, antennasizes, and antenna spacing can all be smaller than those at lowfrequency, thus making it feasible to equip a node with a large numberof antennas. As a result, the beams formed by the large number ofantennas can be very narrow, for example, with beamwidth of 10 deg oreven less. In sharp contrast, in traditional wireless communications,beamwidth is generally much wider, such as tens of degrees. See FIG. 8Afor an illustration of the wider beam pattern 802 with a small number ofantennas in low frequency, and FIG. 8B for an illustration of the narrowbeam pattern 804 with a large number of antennas in high frequency. Ingeneral, it is regarded that narrow beams are a major new feature ofmmWaves. As a general rule of thumb, the beamforming gain by massiveMIMO can be roughly estimated by N×K, where N is the number of transmitantennas and K the receive antennas. This is because the 2-norm of thechannel matrix H scales roughly according to (N×K)^(1/2), and thereforeif the precoding vector by the transmitting node is p, and the combiningvector by the receiving node is w, then the composite channel is w′Hp,and by properly selecting w and p, the composite channel gain in energycan attain N×K, much higher than the case with fewer antennas.

Thus, it can be seen that when considering further evolution of thesmall cell networks, the main scenarios may be small cell networks withabundant resources in both node-density dimension and spectrumdimension, where the spectrum resources may be in high frequency and/orin unlicensed/shared-licensed bands. The small cells are overlaid withwider-area macro cells. Such scenarios may be called hot areas, whichindicate enlarged areas as compared to hot spots. Such hot areas aregenerally deployed and controlled by the network operators. For such hotareas, discontinuous, opportunistic, or on-demand transmissions (andreception) and measurements (of signals and/or various types ofinterference) on flexibly selected resources are needed.

Next we identify some problems we have discovered that may beencountered for some hot area communications. For the small cellsoperating in high-frequency unlicensed/shared-licensed band, the smallcells may need to perform carrier sensing before transmissions. However,as previous discussed, there is a significant difference of the energyemission spatial patterns and interference spatial distributions betweenmmWave and microwave. The interference that may be sensed during thesensing period is likely to be narrow-beam interference (due to thebeamforming done by a large number of antennas), and the transmissionthat may be done is also likely to be narrow-beam transmission. Roughlyspeaking, the communications between two nodes are somewhat (more)similar to those over a dedicated channel, with interference (leakageout of the narrow beam) mainly concentrated along the transmissiondirection. Associated with this is that the spatial distribution ofnodes whose communications may be affected by a narrow beam isconsiderably different than that of nodes whose communications may beaffected by a wider (normal) beam. In other words, the existingcollision avoidance mechanism designed for wider beams may not besuitable for hot area operations. To achieve efficient collisionavoidance in narrow-beam scenarios, existing listen-before-talkmechanism may need to be reexamined and appropriately modified.

For simplicity, consider transmission/reception in the horizontal planeonly; transmission/reception in 3D space can be understood likewise. Seesystem 900 in FIG. 9 with 3 nodes and their ranges with traditional verywide antenna beams. Suppose node 1 is transmitting to node 2. Acollision at node 2 may occur only if an interfering beam from anothernode, called node 3, hits node 2. To avoid the collision, node 1 may nottransmit if it senses node 3 transmitting, and node 3 may not transmitif it senses node 1 transmitting. This is the main intuition behind theCSMA/CA protocol. Note that, however, the so called hidden/exposed nodeproblems are not considered in this thinking; that is, whether thereceiving node 2 can sense from the interfering node 3 or not. Instead,this thinking works well if node 1 and node 2 are “close enough” so thatif node 1 is within/beyond the range of node 3, then node 2 is alsowithin/beyond the range of node 3. Namely, the sensibility of node 3 atnode 1 roughly represents the sensibility of node 3 at node 2. Thisholds in general scenarios, though in some scenarios the hidden/exposednode problems exist.

Now consider an embodiment narrow-beam transmissions system 1000 in highfrequency as illustrated in FIG. 10 with 3 nodes and their ranges withnarrow beams. Again suppose node 1 is transmitting to node 2. Acollision at node 2 may occur only if an interfering beam from node 3hits node 2. However, the precoding for node 3 is such that in generalthe beam of node 3 is not pointing to either node 1 or node 2, and evenif the beam of node 3 hits node 2 (e.g., when it is pointing to node 2or it leaks to node 2 with certain energy), the receiver combining fornode 2 is such that in general the receiver of node 2 is not sensitiveto the transmission from node 1. It may be true that node 2 can sensenode 3 if node 2 adjusts its receiver combining weights to point to node3, but node 2 does not do so since it adjusts its receiver combingweights to point to node 1, which is generally a different direction. Inother words, collision at node 2 may be avoided due to node 2'S highlyspatially selective reception. This implies that node 1 may still beable to transmit to node 2 even if the beam of node 3 hits node 1. Forexample, if node 1 senses node 3 but node 3's beam is not likely to bealigned with node 2'S receiving direction, then node 1 can stilltransmit to node 2 without concerning about collision at node 2.Therefore, the sensing by node 1 (or by node 3, similarly) may beperformed directionally for deciding if a transmission can occur or not.

To better understand this, see system 1100 in FIG. 11 for anillustration of two beams arriving at a node's receiver. If the receiverhas an omni-directional antenna, then both beams are weighted equally inthe receiver. If the receiver can apply combining weights, then it canweigh one beam higher than the other beam. Generally the receiver mayadjust so that it is aligned with the desired beam (say, beam A), and itcan then discount the impact of the interfering beam B. Therefore, beamB may contribute much less to the received power at the node, i.e., theinterfering beam may not be sensible if a certain receiver combiningvector is applied. Note that the vector may be applied in analog domainand/or digital domain; in digital domain the receiver does thepost-processing of the received signals. Moreover, the node may need totransmit towards the direction of beam A, for this purpose it can selectits precoding vector as the receiver combining vector by exploiting thechannel reciprocity.

Essentially the above indicates that the concept of sensibility may bedifferent in scenarios with narrow-beam transmission/reception in highfrequency, and accordingly the sensing should be done differently underthe new sensibility setting.

FIG. 12 is a flowchart of an embodiment method 1200 for spatial-specificcarrier sensing. Method 1200 is in contrast with the traditional carriersensing illustrated in FIG. 5. In an embodiment, before receiving awaveform signal at block 1202 during the sensing time, the node isprovided (e.g., by a certain component of the node, such as thescheduler of the node which allocates transmission resource for anassociated transmission) with a resource-specific receiving pattern atblock 1201, and the node applies the pattern for its receiving. In anembodiment, the resource-specific receiving pattern is aspatial-specific receiving pattern. For example, the pattern may be usedby the node to steer its antennas towards certain directions, or changeits downtilt, etc. In other words, the pattern may specify aspatial-domain antenna pattern. Note that the spatial-domain antennareceiving pattern is only part of the receiver beamforming; thespatial-domain antenna receiving pattern is used to adjust the (analog,RF) phase shifters of the antennas, and it can be used in conjunctionwith the digital processing after the RF chains for receiverbeamforming. For another example, the pattern may specify aspatial-domain antenna pattern and/or a frequency-domain pattern, andthen the node may tune its RF accordingly. In general, thespatial-specific receiving pattern may be extended to resource-specificreceiving pattern which specifies the spatial resource along which theantennas should point to, the frequency resource the receiving should bedone, etc.

At block 1204, after the receive antennas receive the waveform signal atblock 1202, the node performs some (digital) processing after the RFchains. In an embodiment, before the processing at block 1204, the nodeis provided (e.g., by a certain component of the node, such as thescheduler of the node which allocates transmission resource for anassociated transmission) with a spatial-specific processing pattern atblock 1203, and the node applies the pattern for its processing in block1204. For example, the pattern may be used by the node to combine thereceived signals on different antennas so that effectively the receiverforms a beam towards a certain direction in spatial domain. To be morespecific, if there are M RF chains used for the receiving and M receivedsignals are obtained by the RF chains, then the spatial-specificprocessing pattern can be an M-length vector (or multiple M-lengthvectors) to combine the received signals such that the receiverbeamforming points to a desired direction. In general, thespatial-specific processing pattern may be extended to resource-specificprocessing pattern which specifies the spatial resource along which theantennas should point to, the frequency resource the processing shouldbe done, etc.

After the receiver processing at block 1204, the method proceeds toblock 1206 where the receiver generates a decision variable, X andcompares the decision variable, X, with a decision threshold, T. Thedecision variable, X, is generally a scalar number reflecting thereceived energy level along the direction of the composite receiverbeam. The threshold, T, may be determined by a number of factors, suchas the power level of the node, the power level of the associatedtransmission. If, at block 1206, the decision variable, X, does notexceed the threshold, T, then the method 1200 proceeds to block 1210where the channel is considered as “idle on the spatial resource” andhence the node can transmit on this spatial resource; otherwise, themethod 1200 proceeds to block 1208 where the channel is considered asbusy/occupied on the spatial resource and hence the node cannot transmiton this spatial resource.

This embodiment of spatial-specific carrier sensing can be used as thecore of spatial-specific LBT. FIG. 13 is a flow chart of an embodimentmethod 1300 for spatial-specific LBT. The method 1300 begins at block1302 where the node determines a transmission resource. For example,suppose the node is attempting to transmit using a specific transmissionresource; the transmission resource may specify whichtime/frequency/spatial/power resources the transmission will beperformed. For example, the transmission resource specifies the spatialresource along which the transmit antennas should point to, thefrequency resource the transmission should be done, the power level thatthe transmission will use, etc. Specifically, consider the case that theresource specifies the precoding of the transmission; in other words,the node is attempting to transmit toward a certain direction. Then, atblock 1301 and block 1302 associated with the transmission resource(i.e., the beamforming direction of the transmission), the nodegenerates a spatial-specific receiving pattern and/or spatial-specificprocessing pattern. The generated patterns may be such that the receivedsignal is received and processed in a way related to the attemptedtransmission. Some embodiments of the relation between thereceiving/processing patterns and the transmission pattern will be givenlater. For example, the receiving/processing patterns are such that thereceiver beam direction is aligned with the beam direction of thetransmission resource.

At block 1308, spatial-specific carrier sensing is performed, and thenode determines whether the channel is considered as idle orbusy/occupied on the transmission resource (i.e., the beamformingdirection of the transmission in this case). If, at block 1308, thechannel is considered as idle, then the node can transmit on thetransmission resource and the method 1300 proceeds to bock 1312 wherethe node transmits on the resource; otherwise, if, at block 1308, thechannel is busy, the node cannot transmit on the transmission resource,then the method 1300 proceeds to block 1310 where the node does nottransmit on the resource, after which, the method 1300 proceeds to block1302. In the latter case, the node may attempt another transmission onanother transmission resource, e.g., it may simply choose another chooseanother precoding direction, or choose another time (which is thebehavior of conventional LBT), or choose another frequency resource, orchoose another power level of the transmission (e.g. reducing thetransmission power so that the sensing threshold is increased), etc.This new attempted transmission may or may not be actually performeddepending on the sensing result on the new transmission resource. Thenew attempted transmission may be another attempt of the previoustransmission, i.e., it may be for the same data to the same recipient,but using a different direction and/or a different frequency resource,etc. On the other hand, the new attempted transmission may not be thesame as the one; for example, it can be for another recipient. In otherwords, if the initial attempt did not go through due to some othertransmission ongoing on that direction, the node may decide to transmiton a different direction which is generally associated with a differentUE. That is, the node may exploit multi-user diversity when deciding itstransmission resources. After a failed attempt (i.e., an attempt totransmit along some direction but it does not go through), the nodegains knowledge about which direction it cannot transmit, and the nodecan better schedule its next attempted transmission so that it may havea better chance to go through. For example, from the failed attempt, thenode knows that along a direction the received signal is very strong,then the node may choose to avoid this direction as much as possible,such as choosing to transmit to an orthogonal direction.

Alternatively, the node may attempt to transmit on several transmissionresources at the same time, but select only those associated with idlechannels for its actually transmissions. For example, after the nodereceives the waveform signal and the RF chain generates receivedsignals, several different vectors (i.e. spatial-specific processingpatterns) used for combining the received signals can be provided (e.g.,by a certain component of the node). For each vector, a decisionvariable can be generated, and hence the receiver can obtain severaldecision variables. Then the one with the smallest value (relative tothe associated decision threshold) is selected if it does not exceed theassociated threshold, and the associated spatial-specific processingpattern is selected. This pattern may be further associated with atransmission direction, and then the node will transmit on thatdirection. The node may also compute a suitable spatial-specificprocessing pattern for its next transmission, for example, the receiversolves an optimal combining problem given the signals generated by theRF chains, generating a beam direction along which the channel isconsidered as idle, and then transmits along that direction. Forexample, the output of the RF chains may be a vector y, and then thereceiver picks one vector in the null space of the vector y as theoptimal spatial-specific processing pattern, and the next transmissionwill be associated with this pattern. Note that the null space of thevector y generally contains infinite number of vectors, and any of themmay be used as the spatial-specific processing pattern. The node canthen project the directions to its recipients into the null space andpick the one with the largest projection value.

In an embodiment, the node sensing the channel status sets its receivercombining weights to be equal to the precoding for the desiredtransmission, if the receiver antenna number is equal to the transmitterantenna number. In other words, if the interference projected to thedesired transmission direction (by applying the post-combining receiverantenna pattern when sensing the interference) is weak, effectively thenode does not “hear” the interference and it can still transmit.

In an embodiment, the node sensing the channel status sets its receivercombining weights so that the receiver beam direction is aligned withthe beam direction for the desired transmission. Note that the receivermay not use the same number of antennas as the transmitter, but theincoming beam and outgoing beam can still be aligned, though thebeamwidths may not be exactly the same (due to the antenna numberdifference).

In an embodiment, the node sensing the channel status sets its receivercombining weights based on the beam direction for the desiredtransmission. For example, the receiver beam direction for sensing maybe selected to form a certain angle with the transmitter beam directionfor the associated transmission. For another example, the receiver beamdirection for sensing may be selected to form a 0 degree angle and 180degree angle (i.e. two opposite beams) to the transmitter beam directionfor the associated transmission; this may be useful if the interferingnode is lined up with the transmitter and receiver but its location isunknown to the transmitter. For another example, the receiver beamdirection for sensing may be selected as orthogonal to the transmitterbeam direction for the associated transmission.

In an embodiment, the node first senses the channel status by digitallycombining the received signals during the sensing period, and thendecides on the precoding vector for the transmission following thesensing period. In other words, the precoding for the followingtransmission is correlated with the sensed signal. For example, bydigitally processing the received signal, the node identifies certaindirections along which the sensed signal is very weak, and then the nodedecides to transmit along one of these directions. Note that the nodemay have multiple UEs to serve and they are distributed in differentdirections. Therefore, the node may exploit multi-user diversity gain inthis case. Alternatively, the node may decide to beamform in a directionforming a certain angle with the strongest sensed beam direction, suchas orthogonal to the strongest sensed beam direction. In general, theseembodiments specify spatial-resource restricted sensing.

In an embodiment, the node sensing the channel status sets itselectronic downtilt according to the desired transmission downtilt. Inanother embodiment, the node sets its electronic downtilt fortransmission based on the sensed signal.

In an embodiment, the node uses location information to identify itssensing beam direction and/or transmission beam direction. The locationinformation may contain information about the receiving node location,the interfering node location, etc. The location information may beobtained by any location technology, e.g. GPS, or RF signatures, etc.With the location information, the node may build a geographic “map” ofthe surrounding nodes and better adapt its sensing and transmitting beamdirections to avoid collision.

In an embodiment, the node senses on the resources in spatial-frequencydomain based on the resources on which the desired transmission is to beperformed. For example, if the node will transmit along a direction onlyon a subset of the frequency resource, such as a subband, then the nodemay need to sense along the associated sensing direction(s) on thesubband. Note that in this case, other subbands in the channel may beused by the node (for transmissions along other directions) or not usedby the node (e.g., used by WiFi nodes operating on partially overlappedchannels). In another embodiment, the node senses in full bandwidth inmultiple directions, but the node digitally processes the receivedsignal to identify the interference directions in subbands, and thendecides its transmissions on subbands based on the processed results.For example, it may identify a particular band and a beam direction forone of its UEs to receive with potentially lower interference. Insummary, these embodiments specify resource-specific sensing, where theresources can be in spatial-frequency domain.

In an embodiment, the node is desired to transmit more than one stream,such as performing a rank 2 transmission or a multi-user MIMOtransmission. More than one beam needs to be formed for thistransmission, and accordingly, more than one sensing beam needs to beformed during the sensing.

In an embodiment, the threshold used for determine the sensibilityduring the sensing is a power level used to threshold the receivedpost-combing signal. Alternatively, the one-dimensional (scalar)threshold corresponding to a sphere (i.e., non-spatially selective)criterion is replaced by a multi-dimensional (vector or continuousfunction) threshold corresponding a spatially selective criterion. Thethreshold may be different on different subbands. The threshold may alsobe different for different transmission power associated with atransmission, For example, a higher transmission power should beassociated with a lower threshold, such as according to the CCAthreshold level TL formula: TL=−73 dBm/MHz+23−P, assuming a 0 dBireceive antenna and the transmission power P specified in dBm e.i.r.p.

FIG. 14 illustrates a block diagram of an embodiment processing system1400 for performing methods described herein, which may be installed ina host device. As shown, the processing system 1400 includes a processor1404, a memory 1406, and interfaces 1410-1414, which may (or may not) bearranged as shown in FIG. 14. The processor 1404 may be any component orcollection of components adapted to perform computations and/or otherprocessing related tasks, and the memory 1406 may be any component orcollection of components adapted to store programming and/orinstructions for execution by the processor 1404. In an embodiment, thememory 1406 includes a non-transitory computer readable medium. Theinterfaces 1410, 1412, 1414 may be any component or collection ofcomponents that allow the processing system 1400 to communicate withother devices/components and/or a user. For example, one or more of theinterfaces 1410, 1412, 1414 may be adapted to communicate data, control,or management messages from the processor 1404 to applications installedon the host device and/or a remote device. As another example, one ormore of the interfaces 1410, 1412, 1414 may be adapted to allow a useror user device (e.g., personal computer (PC), etc.) tointeract/communicate with the processing system 1400. The processingsystem 1400 may include additional components not depicted in FIG. 14,such as long term storage (e.g., non-volatile memory, etc.).

In some embodiments, the processing system 1400 is included in a networkdevice that is accessing, or part otherwise of, a telecommunicationsnetwork. In one example, the processing system 1400 is in a network-sidedevice in a wireless or wireline telecommunications network, such as abase station, a relay station, a scheduler, a controller, a gateway, arouter, an applications server, or any other device in thetelecommunications network. In other embodiments, the processing system1400 is in a user-side device accessing a wireless or wirelinetelecommunications network, such as a mobile station, a user equipment(UE), a personal computer (PC), a tablet, a wearable communicationsdevice (e.g., a smartwatch, etc.), or any other device adapted to accessa telecommunications network.

In some embodiments, one or more of the interfaces 1410, 1412, 1414connects the processing system 1400 to a transceiver adapted to transmitand receive signaling over the telecommunications network. FIG. 15illustrates a block diagram of a transceiver 1500 adapted to transmitand receive signaling over a telecommunications network. The transceiver1500 may be installed in a host device. As shown, the transceiver 1500comprises a network-side interface 1502, a coupler 1504, a transmitter1506, a receiver 1508, a signal processor 1510, and a device-sideinterface 1512. The network-side interface 1502 may include anycomponent or collection of components adapted to transmit or receivesignaling over a wireless or wireline telecommunications network. Thecoupler 1504 may include any component or collection of componentsadapted to facilitate bi-directional communication over the network-sideinterface 1502. The transmitter 1506 may include any component orcollection of components (e.g., up-converter, power amplifier, etc.)adapted to convert a baseband signal into a modulated carrier signalsuitable for transmission over the network-side interface 1502. Thereceiver 1508 may include any component or collection of components(e.g., down-converter, low noise amplifier, etc.) adapted to convert acarrier signal received over the network-side interface 1502 into abaseband signal. The signal processor 1510 may include any component orcollection of components adapted to convert a baseband signal into adata signal suitable for communication over the device-side interface(s)1512, or vice-versa. The device-side interface(s) 1512 may include anycomponent or collection of components adapted to communicatedata-signals between the signal processor 1510 and components within thehost device (e.g., the processing system 1400, local area network (LAN)ports, etc.).

The transceiver 1500 may transmit and receive signaling over any type ofcommunications medium. In some embodiments, the transceiver 1500transmits and receives signaling over a wireless medium. For example,the transceiver 1500 may be a wireless transceiver adapted tocommunicate in accordance with a wireless telecommunications such as acellular protocol (e.g., long-term evolution (LTE), etc.), a wirelesslocal area network (WLAN) protocol (e.g., Wi-Fi, etc.), or any othertype of wireless protocol (e.g., Bluetooth, near field communication(NFC), etc.). In such embodiments, the network-side interface 1502comprises one or more antenna/radiating elements. For example, thenetwork-side interface 1502 may include a single antenna, multipleseparate antennas, or a multi-antenna array configured for multi-layercommunication, e.g., single input multiple output (SIMO), multiple inputsingle output (MISO), multiple input multiple output (MIMO), etc. Inother embodiments, the transceiver 1500 transmits and receives signalingover a wireline medium, e.g., twisted-pair cable, coaxial cable, opticalfiber, etc. Specific processing systems and/or transceivers may utilizeall of the components shown, or only a subset of the components, andlevels of integration may vary from device to device.

In an embodiment, a method in a first communication node for providingcontention-based transmission from the first communication node in anetwork to a second communication node includes determining, by thefirst communication node, a transmission direction, the transmissiondirection characterized by a digital beamforming direction and an analogbeamsteering direction; performing, by the first communication node,spatial-specific carrier sensing in accordance with a sensing directionassociated with the transmission direction; determining, by the firstcommunication node, a channel status of a channel along the sensingdirection according to the spatial-specific carrier sensing; andtransmitting, by the first communication node, a transmission along thetransmission direction. The transmission direction here may notnecessarily be the line-of-sight direction between the first node andthe second node. In an embodiment, the sensing direction is along thetransmission direction or along a direction opposite of the transmissiondirection. In an embodiment the beamforming direction for bothtransmitting and receiving is generated by digital weights applied tothe RF chains by the baseband. In an embodiment, the analog beamsteeringdirection, for both transmitting and receiving, is generated by phaseshifters. In other words, the direction is associated with the“processing pattern” for digital beamforming and/or “receiving pattern”for analog beam steering. Performing spatial-specific carrier sensing inaccordance with the transmission direction includes generating, by thefirst communication node, at least one of a spatial-specific receivingpattern and a spatial-specific processing pattern in accordance with thesensing direction; receiving, by the first communication node, awaveform signal from one or more third nodes in accordance with thespatial-specific receiving pattern; processing, by the firstcommunication node, in accordance with the spatial-specific processingpattern; and generating, by the first communication node, a decisionvariable for determining the channel status of the channel along thesensing direction according to the waveform signal and the at least oneof the spatial-specific receiving pattern and the spatial-specificprocessing pattern. In an embodiment, the waveform signal can be anysignal sent by any other nodes. Such a signal may be seen asinterference to the communications from the first node to the secondnode. In an embodiment, the waveform signal is a superposition oftransmissions from the one or more third nodes. In an embodiment, whensuch a signal (interference) is strong, the first node may not want totransmit along that direction. In an embodiment, the channel status ofthe channel along the sensing direction is determined by comparing thedecision variable against a decision threshold, wherein the channel isconsidered idle along the transmission direction when the decisionvariable is smaller than the decision threshold. In an embodiment, thedecision threshold is determined based on at least one of thetransmission power for the transmission, the frequency band (orsubbands) for the transmission, and the transmission direction. Thespatial-specific receiving pattern is associated with a receiver beamdirection and is associated with a set of receiver phase shift valuesapplied to the receiver analog phase shifters. In an embodiment, thespatial-specific processing pattern is a receiver combiningvector/matrix associated with a precoding vector/matrix of thetransmission direction applied in the digital domain. In an embodiment,the resource-specific receiving pattern and the resource-specificprocessing pattern are patterned such that a composite receivercombining a direction in a spatial domain is aligned with a compositebeamforming direction plus a beamsteering of the transmission directionin the spatial domain. In an embodiment, the spatial-specific processingpattern is a receiver combining vector/matrix, wherein determining thereceiver combining vector/matrix comprises obtaining a waveform receivedby the an analog components of the receive antennas in accordance withthe spatial-specific receiving pattern; determining a plurality ofcombining vectors/matrices; generating a plurality of decision variablesaccording to the plurality of combining vectors/matrices by applying thevectors/matrices to the waveform; and selecting one of the plurality ofcombining vectors/matrices as the receive combining vector/matrixaccording to a smallest one of the plurality of decision variable. Inother words, when the baseband digital unit processes the receivedwaveform, it may apply different digital combining vectors/matrices(e.g., p₁, p₂, p₃, . . . , where each p_(i) is vector/matrix) to thewaveform, generating different decision variables X₁, X₂, X₃, . . . .Then the digital combining vector/matrix associated with the smallest Xis used, as that direction has the least amount of detected transmissionactivities. An optimization problem may be solved by the baseband tofind the optimal direction among all possible directions. In anembodiment, performing spatial-specific carrier sensing in accordancewith the sensing direction includes determining a receiver combiningvector/matrix, wherein determining the receiver combining vector/matrixincludes generating, by the first communication node, a spatial-specificreceiving pattern and an initial spatial-specific processing pattern inaccordance with the sensing direction; obtaining a waveform received byanalog components of the receive antennas in accordance with thespatial-specific receiving pattern; determining a plurality of combiningvectors/matrices associated with a plurality of spatial-specificprocessing patterns; generating a plurality of decision variablesaccording to the plurality of combining vectors/matrices by applying thevectors/matrices to the waveform; and selecting one of the plurality ofcombining vectors/matrices as the receive combining vector/matrixaccording to a smallest one of the plurality of decision variables,wherein the selected receive combining vector/matrix defines theselected spatial-specific processing pattern, and the selected sensingdirection is characterized by the spatial-specific receiving pattern andthe selected spatial-specific processing pattern, and the channel statusof the channel along the selected sensing direction is determined by thedecision variable generated by the selected spatial-specific processingpattern; determining, by the first communication node, a newtransmission direction associated with the selected sensing direction;and transmitting, by the first communication node, a transmission alongthe new transmission direction.

In an embodiment, a first communication node for providingcontention-based transmission from the first communication node in anetwork to a second communication node includes a processor and anon-transitory computer readable storage medium storing programming forexecution by the processor, the programming including instructions to:determine a transmission direction, the transmission directioncharacterized by a digital beamforming direction and an analogbeamsteering direction; perform spatial-specific carrier sensing inaccordance with the transmission direction; determine a channel statusof a channel along the transmission direction according to thespatial-specific carrier sensing; and transmit a transmission along thetransmission direction.

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments, as well as other embodiments of the invention,will be apparent to persons skilled in the art upon reference to thedescription. It is therefore intended that the appended claims encompassany such modifications or embodiments.

What is claimed is:
 1. A method for wireless communications by a firstcommunication node in a network, the method comprising: generating, bythe first communication node, at least one of a spatial-specificreceiving pattern and a first spatial-specific processing pattern;receiving, by the first communication node, a waveform signal from oneor more second nodes in accordance with the at least one of thespatial-specific receiving pattern or the first spatial-specificprocessing pattern; determining, by the first communication node, asecond spatial-specific processing pattern and a channel status of achannel, wherein the channel status of the channel is according to theat least one of the spatial-specific receiving pattern and the secondspatial-specific processing pattern; and transmitting, by the firstcommunication node, a signal along a transmission direction, wherein thetransmission direction is in accordance with the at least one of thespatial-specific receiving pattern and the second spatial-specificprocessing pattern.
 2. The method of claim 1, further comprisingsensing, by the first communication node, in a sensing direction,wherein the sensing direction is associated with the transmissiondirection.
 3. The method of claim 2, wherein the sensing direction isalong the transmission direction.
 4. The method of claim 2, wherein thesensing direction is along a direction opposite of the transmissiondirection.
 5. The method of claim 1, wherein the waveform signalcomprises a superposition of transmissions from the one or more secondnodes.
 6. The method of claim 1, wherein the channel status of thechannel is determined by comparing a decision variable against adecision threshold, and wherein the channel is considered idle along thetransmission direction when the decision variable is smaller than thedecision threshold.
 7. The method of claim 6, wherein the decisionthreshold is determined based on at least one of the factors of atransmission power of the transmission, a frequency band for thetransmission, or the transmission direction.
 8. The method of claim 1,wherein the spatial-specific receiving pattern is associated with areceiver beam direction and a set of receiver phase shift values appliedto receiver analog phase shifters.
 9. The method of claim 1, wherein thefirst spatial-specific processing pattern is a first receiver combiningvector or combining matrix associated with a first precodingvector/matrix of the transmission direction applied in the digitaldomain.
 10. The method of claim 9, wherein the second spatial-specificprocessing pattern is a second receiver combining vector or combiningmatrix associated with a second precoding vector/matrix of thetransmission direction applied in the digital domain.
 11. A firstcommunication node comprising: a processor; and a non-transitorycomputer readable storage medium storing programming for execution bythe processor, the programming including instructions to: generate atleast one of a spatial-specific receiving pattern and a firstspatial-specific processing pattern; receive a waveform signal from oneor more second nodes in accordance with the at least one of thespatial-specific receiving pattern or the first spatial-specificprocessing pattern; determine a second spatial-specific processingpattern and a channel status of a channel, wherein the channel status ofthe channel is according to the at least one of the spatial-specificreceiving pattern and the second spatial-specific processing pattern;and transmit a signal along a transmission direction, wherein thetransmission direction is in accordance with the at least one of thespatial-specific receiving pattern and the second spatial-specificprocessing pattern.
 12. The first communication node of claim 11,wherein the instructions further comprise to sense in a sensingdirection, wherein the sensing direction is associated with thetransmission direction.
 13. The first communication node of claim 12,wherein the sensing direction is along the transmission direction. 14.The first communication node of claim 12, wherein the sensing directionis along a direction opposite of the transmission direction.
 15. Thefirst communication node of claim 11, wherein the waveform signalcomprises a superposition of transmissions from the one or more secondnodes.
 16. The first communication node of claim 11, wherein the channelstatus of the channel is determined by comparing a decision variableagainst a decision threshold, and wherein the channel is considered idlealong the transmission direction when the decision variable is smallerthan the decision threshold.
 17. The first communication node of claim16, wherein the decision threshold is determined based on at least oneof the factors of a transmission power of the transmission, a frequencyband for the transmission, or the transmission direction.
 18. The firstcommunication node of claim 11, wherein the spatial-specific receivingpattern is associated with a receiver beam direction and a set ofreceiver phase shift values applied to receiver analog phase shifters.19. The first communication node of claim 11, wherein the firstspatial-specific processing pattern is a first receiver combining vectoror combining matrix associated with a first precoding vector/matrix ofthe transmission direction applied in the digital domain.
 20. The firstcommunication node of claim 19, wherein the second spatial-specificprocessing pattern is a second receiver combining vector or combiningmatrix associated with a second precoding vector/matrix of thetransmission direction applied in the digital domain.